1. Field of the Invention
The present invention relates to a reciprocating internal combustion engine having poppet valves which are driven by a camshaft. The valves may be disabled selectively, so as to effectively change the displacement of the engine.
2. Disclosure Information
Dual displacement engines characterized by the capability to deactivate the intake and exhaust valves for particular cylinders, so as to increase fuel economy, are known in the art. One method for deactivating valves involves a hydraulic control of the valve actuation systems. Unfortunately, hydraulic control is rendered more expensive because of the need to provide separate control circuits, including control valves, for both the intake and exhaust valves. In other words, electronic control valves must be provided to meter or restrict the flow of oil to the valve operators for both intake and exhaust valves. In a V-type engine, this commonly means that four electronic control valves must be employed to deactivate various cylinders of the engine.
It would be desirable to provide a deactivation system requiring only a single valve for each bank of cylinders, while preserving the phasing necessary to properly deactivate and reactivate the cylinders. In general, phasing is best accomplished by deactivating the exhaust valve first for any particular cylinder, followed by deactivation of the intake valve for the same cylinder. Deactivation of the intake and exhaust valves in this sequence will trap a burnt charge in the engine's cylinder, preventing excess vacuum in the cylinder, which could pull in crankcase gases. This phased deactivation of the exhaust and intake valves will avoid a puff of unburned hydrocarbon when the cylinders are reactivated. Heretofore, this phasing aspect has, as noted above, required multiple control valves. The present invention avoids the need for multiple deactivation control valves for any particular bank of cylinders in an engine.